Method and apparatus for producing an annular collar from a pipe in a hot state

ABSTRACT

A method of producing an annular tubular collar from a tube or pipe in a hot state and without introducing transverse forces which tend to deform the cross-section of the tube and using pairs of opposed rollers each pair including an inside roller arranged on the inside of the pipe bend and an outside roller arranged on the outside of the bend, comprises regulating the peripheral speed of the inside and outside rollers to produce a braking effect by the inside rollers on the tube. The apparatus includes at least three pairs of oppose rollers between which the pipe to be bent is directed, and, in one embodiment, the inside rollers are made with a relatively small diameter compared to the outside rollers and in another arrangement, the inside rollers have a larger diameter than the outside rollers. In each case, the inside rollers are driven at a peripheral speed so that they provide a braking action on the tube to effect an imposition of a longitudinal force directed opposite to the direction of passage to enhance the bending of the pipe and to reduce transverse forces acting on the pipe which tends to distort its crosssection.

United States Patent 1191 Ehm 1451 July .3, 1973 1 METHOD AND APPARATUS FOR PRODUCING AN ANNULAR COLLAR FROM A PIPE TN A HOT STATE Karl Horst Ehm, Mulheim/Ruhr, Germany [75] Inventor:

[73] Assignee: Demag Aktiengesellschaft, Duisberg,

Germany [22] Filed: June 21, .1971

211 App]. NO. 154,775

[30] Foreign Application Priority Data July 3', 1970 Germany P 20 32 937.7

[52] US. Cl. 72/166, 72/366 [51 Int. Cl 1321:! 9/10 [58] Field of Search 72/170, 166, 135, 72/369, 173-175 [56] References Cited UNITED STATES PATENTS 3,566,654 3/1971 Adams at a] 72/170 x 3,036,622 5/1962 1m: 72/170 x 2,327,706 8/1943 Halstea 72/166 xv 7/1909 Schneider 72/175 Primary Examiner-Milton S. Mehr Attorney-John J. McGlew et al.

[57] ABSTRACT A method of producing an annular tubular collar from a tube or pipe in a hot state and without introducing transverse forces which tend to deform the crosssection of the tube and using pairs of opposed rollers, each pair including an inside roller arranged on the inside of the pipe bend and an outside roller arranged on the outside of the bend, comprises regulating the pe-' ripheral speed of the inside and outside rollers to produce a braking effect by the inside rollers on thetube. The apparatus includes at least three pairs of oppose rollers between which the pipe to be bent is directed,

and, in one embodiment, the inside rollers are made with a relatively small diameter compared to the outside rollers and in another/arrangement, the inside rollers have a larger diameter than the outside rollers. In each case, the inside .rollers are driven at a peripheral speed so that they provide a braking action on the tube to effect an. imposition of a longitudinal force directed opposite to the direction of passage to enhance the bending of the pipe and to reduce transverse forces acting on the pipe which tends to distort its cross-section.

9 Clairns, 3 Drawing Figures PATENTEBJUL3 I573 3.742.748

lm en KARL How- BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates in general to the apparatus and method for forming tubular elements or pipes and, in particular, to a new and useful apparatus and method for forming pipes into coils and in which the driving speed of interior and exterior rollers is regulated to reduce the transversely acting forces which tend to distort the pipe cross-section.

2. Descriptionof the Prior Art The present invention is an improvement over German Pat. application P 19 36 515.2 corresponding to U.S. Pat. Application Ser. No. 52,796, filed July 7, 1970, now abandoned. The aforementioned patent describes a method of producing a coil of pipe from a pipe in a hot state. The method is preferably carried out following the production of the pipe in the hot state in which there is a stretch reduction. The pipe is bent before the turns are laid with a bending radius which corresponds to the respective turn of the annular collar to be formed. The same velocity is imparted to the pipe during the bending and the laying of the turn as the pipe had immediately before it was moved into association with the bending apparatus. The arrangement for carrying out the method is characterized by a bending apparatus which has an adjustable bending radius. This bending apparatus comprises substantially three pairs of opposed rolls between which the pipe is bent and which form a so-called bending triangle or a plurality of such triangles.

In the production of coils from pipes with outside diameters which are for example greater than 25 mm and which have a normal wall thickness, there is a tendency for cross-sectional deformations to appear during the bending by the operation of the bending apparatus and this particularly resultsin so-called-ovaling. This ovaling of the pipe is caused primarily by stresses occurring in the pipe during the bending by means of the bending triangles and which are caused by transverse forces whose size and effect are determined by the resistance moment and also by the cross-section of the pipe. Ovaling is inadmissable for many uses or it interferes with the further processing of the pipes.

It is known to bend pipes about a rotatable molded bending piece. For this bending operation, the front end of the pipe is clamped with the molded bending piece and wound around the periphery of the piece during the rotation thereof. In this bending operation, ovaling of the originally circular pipe cross-section can hardly be avoided.

In order to avoid this disadvantage, it has been suggested that the rear straight section of the pipe should be adjusted during the bending operation to an additional sliding force which is variable in size and uniform over the pipe cross-section and which acts in the longitudinal direction of the pipe as a pressure in the direction of the molded bending piece.

SUMMARY OF THE INVENTION This invention provides an improved arrangement of the apparatus disclosed in the previously mentioned applications, so that the ovaling of the cross-section appearing during the bending is effectively prevented durconsideration that the transverse forces extended bying the production of the annular collar, or at least it is substantially reduced. The invention starts from the the bending apparatus can be reduced if it is possible to produce the bending moment which is necessary for bending in any other way.

The method of the invention provides the production of a continuous coil from a pipe in a hot state where the pipe arrives preferably from a processing device arranged ahead of the bending operation and it is bent before the turn'is laid on the bending apparatus with a bending radius which corresponds to the radius of the collar to be formed. The same velocity is imparted to the pipe during the bending and the laying of the turn which the pipe has immediately before'the bending as set forth in the patent mentioned previously. It is char acterized in that the longitudinal forces acting on the pipe during the bending which vary in size and direction over the pipe cross-section are so directed by the apparatus that a bending moment enhancing the desired bending of the pipe is exerted by them. The application of these additional longitudinal forces on the pipe is effected by driving at least some of the bending and counter-rollers such that there is braking effect on the interior surface of the collar being formed during the bending which is produced different circumferential velocities. The circumferential velocities of the 'rollers are arranged on the outside of the pipe bend is greater than that of the rollers arranged on the inside of the pipe bend. The adjustment of the circumferential velocity is determined by the torque of the individual rollers which is to be transmitted and which is necessary for the application of the longitudinal forcesgln comparison to the known method wherein a rotatable molded bending piece is employed in which the longitudinal forces act on the end which is not to be bent and pushes the pipe into the device, it is possible with the invention to reduce the transverse forces for bending.

In order to carry out the method, the invention provides an arrangement which is characterized by inside and outside rollers which in respect to the collar being 7 formed, act on the pipe so that there is a braking effect arrangement, the rollers arranged outside the bend have a larger radius than those arranged inside the bend of the pipe and all of the rollers are driven jointly to result in different circumferential velocities in order to produce the desired bending moment which is'applied by the frictional drag forces by the slower speed of theinside rollers.

With certain geometric ratios of the pipe, itwas found advantageous to provide the rollers on the inside of the pipe bend with a very large diameter so that the pipe is supported over a great length during the bending. It is therefore suggested that the'rollers inside the bend be provided with a larger diameter than the rollers outside the bend. For this case, when the rollers are used which have the diameter inside the bend as outside, the rollers are driven individually or in groups with variable speed gears.

Accordingly, it is an object of the invention to provide an improved method of bending pipe which includes engagingthe pipe both along the inside of the bend and the outside of the bend by opposing pairs of rollers which are driven'at circumferential speeds such that the rollers act on the pipe without producing transverse forces which adversely effect the cross-section of the pipe being formed.

A further object of the invention is to provide an apparatus for bending pipe which includes a plurality of sets of opposed rollers with the ones arranged on the inside of the bend being driven at a slower peripheral speed than the ones on the outside of the bend in order to counteract the setting up of transverse forces.

A further object of the invention is to provide a device for bending pipe which is simple in design, rugged in construction and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operat ing advantages and specific objects attained by its uses, reference should be had to the accompanying drawing and descriptive matter in which there are illustrated preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. I is a partial section through a bending apparatus constructed in accordance with the invention;

FIG/2 is a view similar to FIG. 1 but showing inside bending rollers of larger diameter than the outside bending rollers; and

FIG. 3 is a section taken along the line IIIlII of FIG. 2.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, in particular, the invention embodied therein comprises a bending apparatus, generally designated 10, for bending a tube or pipe 1 into a coil after is emerges from the stretch-reducing rolling mill and is still in a hot condition. The bending apparatus 10 comprises a plurality of pairs, for example, three pairs of opposed rolls, each pair including an inside roll 5 and an outside roll 4. When the pipe is passed through the apparatus from left to right, as shown in FIG. 1, it undergoes a bending which is effected by the arrangement of the rollers. The bent pipe which emerges from the bending apparatus is fed to a reel pot (not shown) in which the pipe turns are laid to form a continuous coil.

The pipe 1 can be considered in the bending range an a beam on two supports with an individual force arranged between them. The bending moment is effected by the individual forces applied by the central inside roller 5 on the pipe 1 in connection with the supporting forces of the outer rollers 4. These forces which are perpendicular to the pipe axis produce so-called transverse forces in the pipe and can also deform the circular cross-section of the pipe.

In accordance with the method of the invention, in order to reduce the tendency toward the deformation of the circular cross-section of the pipe, the inside rollers and the outside rollers are operated such as to introduce longitudinal forces into the pipe by the action of friction between the pipe and the rollers. The longitudinal forces are produced by braking the rollers 5 on the inside of the bend in comparison to the movement forces produced by the outside rollers 4. The braking force is a longitudinal force directed opposite to the direction of pipe passage and produces tensile forces outside the bend which are directed in the direction of the passage of the pipe. These paired longitudinal forces enhance the bending of the pipe and reduce the transverse forces which act upon it. The transverse forces cannot be completely eliminated since it is not possible to transmit longitudinal forces without some transverse forces. They are reduced, however, to such an extent that deformations of the pipe are avoided in all circumstances with the exception of very thin-walled pipes.

The different longitudinal forces are produced as follows:

Starting from a circumferential velocity of the rollers which is equal to the mean longitudinal velocity of the pipe 1 to be bent, the circumferential velocities of the inside rollers 5 which are arranged inside the pipe is reduced more than corresponds to the effective longitudinal velocity of the pipe 1 in the pressure zone 3 so that they have a braking effect on the pipe 1. The circumferential velocities of the outside rollers 4 which are arranged outside the pipe bend and which engage the pipe 1 in a tension zone 2 are correspondingly increased.

The adjustment of the circumferential velocities of the inside rollers and the outside rollers 4 is effected by taking into account the respective roller diameters and the rotational speed, or when the speed is to be kept at a constant rotational speed, by employing different diameters for the inside rollers 5 and the outside rollers 4.

As shown in the embodiment of FIG. 1, the inside rollers 5 have a smaller diameter than the outside rollers 4 so that when these rollers are driven at the same speed, there is a retarding effect on the inside of the bend causing a frictional force to act in the longitudinal direction on the pipe 1.

In the embodiment of FIG. 2, the inside rollers 5' are of a large diameter than the outside rollers 4', and they must be driven either individually or in groups at variable speeds in order to accomplish the frictional impartation of force at the inside of the bend as in the previous case.

In the case of the individual or group driving of the rollers, the speed is controlled in accordance with the torque which is measured on the individual rollers or the measured on the individual rollers or the measured current consumption of the driving motors may give an indication of this.

What is claimed is:

1. A method of producing an annular tubular coil from a tube in a hot state and without introducing transverse forces which tend to deform the crosssection of the tube after the pipe has preferably been subjected to a pipe processing machine in which it is initially bent but before the turn is laid to form the pipe into a coil and using pairs of opposed rollers each pair including an inside roller arranged on the inside of the bend and an outside roller arranged on the outside of the bend for forming the coil, comprising feeding the pipe with a velocity which is comparable to the velocity the pipe had immediately before the bending between justed to produce a braking effect by the inside rollers on the tube.

3. A method, according to claim 2., wherein the torque acting on the rollers is measured and the inside rollers and the outside rollers are driven at speeds in accordance with the measured torque.

4. A device for producing an annular tubular collar from a tube in a hot state, comprising a plurality of pairs of opposed inside and outside rollers arranged to define a bending path therebetween through which the pipe is adapted to pass, and means for driving at least one pair of said rollers to drive the inside rollers at a different peripheral speed than the outside rollers.

5. A device, according to claim 4, wherein said drive means drives said inside rollers at a speed to produce a braking effect by'said inside rollers on the pipe.

6. A device, according to claim 4, wherein said inside rollers are of a smaller diameter than the outside rollers.

7. A device, according to claim 4, wherein the inside rollers are of a larger diameter than the outside rollers.

8. A device, according to claim 4, including means for driving the inside rollers at a different speed from said outside rollers.

9. A device, according to claim 4, wherein said inside and outside rollers are arranged in groups and each group being driven at a different speed. 

1. A method of producing an annular tubular coil from a tube in a hot state and without introducing transverse forces which tend to deform the cross-section of the tube after the pipe has preferably been subjected to a pipe processing machine in which it is initially bent but before the turn is laid to form the pipe into a coil and using pairs of opposed rollers each pair including an inside roller arranged on the inside of the bend and an outside roller arranged on the outside of the bend for forming the coil, comprising feeding the pipe with a velocity which is comparable to the velocity the pipe had immediately before the bending between opposed pairs of the rollers while driving and regulating the peripheral speed of the rollers to produce a force on the pipe to produce a bending moment on the pipe to enhance the desired bending of the pipe.
 2. A method, according to claim 1, wherein the peripheral speed of the inside and the outside rollers is adjusted to produce a braking effect by the inside rollers on the tube.
 3. A method, according to claim 2, wherein the torque acting on the rollers is measured and the inside rollers and the outside rollers are driven at speeds in accordance with the measured torque.
 4. A device for producing an annular tubular collar from a tube in a hot state, comprising a plurality of pairs of opposed inside and outside rollers arranged to define a bending path therebetween through which the pipe is adapted to pass, and means for driving at least one pair of said rollers to drive the inside rollers at a different peripheral speed than the outside rollers.
 5. A device, according to claim 4, wherein said drive means drives said inside rollers at a speed to produce a braking effect by said inside rollers on the pipe.
 6. A device, according to claim 4, wherein said inside rollers are of a smaller diameter than the outside rollers.
 7. A deviCe, according to claim 4, wherein the inside rollers are of a larger diameter than the outside rollers.
 8. A device, according to claim 4, including means for driving the inside rollers at a different speed from said outside rollers.
 9. A device, according to claim 4, wherein said inside and outside rollers are arranged in groups and each group being driven at a different speed. 